Get domain name from given url

Given a URL, I want to extract domain name(It should not include 'www' part). Url can contain http/https. Here is the java code that I wrote. Though It seems to work fine, is there any better approach or are there some edge cases, that could fail.

If you want to parse a URL, use java.net.URI. java.net.URL has a bunch of problems -- its equals method does a DNS lookup which means code using it can be vulnerable to denial of service attacks when used with untrusted inputs.

Though It seems to work fine, is there any better approach or are there some edge cases, that could fail.

Your code as written fails for the valid URLs:

httpfoo/bar -- relative URL with a path component that starts with http.

HTTP://example.com/ -- protocol is case-insensitive.

//example.com/ -- protocol relative URL with a host

www/foo -- a relative URL with a path component that starts with www

wwwexample.com -- domain name that does not starts with www. but starts with www.

Hierarchical URLs have a complex grammar. If you try to roll your own parser without carefully reading RFC 3986, you will probably get it wrong. Just use the one that's built into the core libraries.

If you really need to deal with messy inputs that java.net.URI rejects, see RFC 3986 Appendix B:

Appendix B. Parsing a URI Reference with a Regular Expression

As the "first-match-wins" algorithm is identical to the "greedy"
disambiguation method used by POSIX regular expressions, it is
natural and commonplace to use a regular expression for parsing the
potential five components of a URI reference.

The following line is the regular expression for breaking-down a
well-formed URI reference into its components.